Follow Illinois, not Wisconsin, to slow spreading CWD

As chronic wasting disease continues its spread in white-tailed deer across the state and continent, two things are becoming clear: First, if you're a Wisconsin hunter, your odds of killing a CWD-positive deer are steadily increasing.

And second, when natural resource agencies consider strategies to deal with CWD discoveries in their states, the example provided by Illinois — not Wisconsin — is the top choice.

Data from the last year show the prevalence of CWD in Illinois has remained relatively low and stable, at slightly more than 1%, while in Wisconsin, the disease has continued to increase to about 6%.

The states share a border but not CWD management strategies.

Since the disease was discovered in both states in 2002, the Illinois Department of Natural Resources has worked to decrease deer numbers in areas CWD is present. The effort has included sharpshooters and increased hunting permits.

Although the Wisconsin DNR initially attempted to eradicate the disease with aggressive measures, including sharpshooters and longer hunting seasons, it now uses only monitoring and surveillance.

The difference in CWD prevalance rates in the two states is due mostly to management strategy, according to University of Illinois researchers Jan Novakofski and Michelle Green.

The pair published a 2013 paper titled, "The Importance of Localized Culling in Stabilizing Chronic Wasting Disease Prevalence in White-Tailed Deer Populations" in Preventive Veterinary Medicine.

Novakofski said after Wisconsin officials changed their strategy, the CWD prevalence rates increased and are still increasing.

Meanwhile, Illinois has remained committed to reducing deer in areas with known CWD-positive animals. The IDNR also is testing deer for CWD in a wide area, hoping to find any new disease sites.

For the sampling year ending June 30, the CWD prevalence rate in Illinois was 1.2%, according to Paul Shelton, forest wildlife manager for the Illinois Department of Natural Resources.

"This is a very challenging issue," Shelton said. "We can't declare victory, but we can say that the work we've been doing has helped keep the rates lower than they otherwise would be."

Chronic wasting disease is a spongiform encephalopathy similar to mad cow disease and scrapie. It is caused by an abnormal prion and can take years to develop but is always fatal. It was first discovered in captive mule deer in Wyoming in the 1960s and has since spread to at least 22 states.

Much has been learned in recent years about prion diseases. In the case of CWD, it is now known the prion is found in muscle tissue as well as plants.

The disease is contagious and found in deer, elk and moose. It has not been linked to human disease, but the Centers for Disease Control and Prevention recommends not eating the meat from CWD-positive animals.

The Wisconsin Division of Public Health recommends that venison from deer harvested from CWD affected areas not be consumed or distributed until test results are negative.

As the disease continues to spread in Wisconsin, more hunters will have to confront decisions about testing.

"I know it's coming," said Ralph Fritsch, 69, of Townsend, who hunts deer in Oconto County and has served on wildlife panels for the Wisconsin Wildlife Federation and Wisconsin Conservation Congress. "Maybe not in my lifetime, but it's coming. It concerns me, absolutely. I wish there was more being done to prevent its spread in Wisconsin."

This year marks an unhappy milestone in Wisconsin's CWD history. For the first time, more than half of the state — 38 counties — is classified as "CWD-affected" going into the fall hunting season.

Baiting and feeding of deer is prohibited in the 38 counties.

Among all deer sampled statewide in Wisconsin in 2014, 331 of 5,460 tested positive for CWD, for a prevalence rate of 6%.

But the rates are much higher in areas where the disease has been detected for more than a decade.

Since 2002, CWD prevalence in the DNR's western monitoring area has shown an overall increasing trend in all sex and age classes, according to the agency.

During the past 13 years, prevalence in adult males has risen from 8% to 10% to over 25% and in adult females from about 3 to 4% to more than 10%. During that same time, CWD rates in yearling males have increased from 2% to 8% and in yearling females from 2% to 7%, according to DNR statistics.

In an area of Iowa County, near the site the disease was discovered in 2002 in Wisconsin, the CWD-positive rate of adult male deer is nearly 40%.

As new CWD "sparks" are found in wild deer or at captive facilities — an Eau Claire County deer farm is the most recent to have a CWD-positive animal — the disease is no longer a local or regional issue.

The experiences of Wisconsin and Illinois over the last 13 years are informing resource managers in other states. The success at keeping prevalence rates relatively low and stable in Illinois have impressed wildlife biologists across the nation.

Chronic wasting disease was detected at a captive facility in Michigan in 2008. And this year, the first wild deer in Michigan with CWD were found in a suburb of East Lansing.

The response? Michigan officials are using sharpshooters to cull deer in the area, as well as issuing more permits to hunters and landowners. They are performing CWD tests on all deer killed in the reduction effort as well as car-killed deer in the vicinity.

"This is as complex a management issue as you're likely to find," said Shelton of the Illinois DNR. "It requires working with landowners, hunters, legislators and others. But if we're going to have a chance at some level of success, we've decided to keep on this path."